It seems that the Anno Aries years was result of totally botched research and bad math. The movement of the Spring Equinox in stars was figured out on 140AD, but someone in the Lions Rampart did misinterpret it as 140BC as 1 A.A. The 140BC is within Ariesian Age, while 1AD forward the Age is Pisces in Zodiac calendar.
Why I am doing this? Creating the Ars Magica campaign tool allowing to use both Hermetic, Julian and Gregorian reckoning for dates and seasons...
Adding Islamic calendar is trivial, and I was considering adding both Islamic and Hebrew calendars to it later first creating Hermetic and Julian. The hardest part would be getting Islamic amd Hebrew month names because I cannot Islamic nor Hebrew script.